Many natural and synthetic materials are known to be useful as lubricants, their utility in particular applications depending on factors such as their stability and viscosity under the conditions of use, their pour points, and their compatibility with any materials with which they will be used.
In refrigeration applications (e.g., home-use or industrial-use refrigerators, freezers, or air conditioners for buildings, automobiles, airplanes, and other vehicles), mineral oils have usually been the lubricants of choice in the past since--in addition to being inexpensive and having other desirable properties--they are compatible with the chlorofluorocarbons that have most commonly been employed as refrigerants. However, mineral oils are incompatible with 1,1,1,2-tetrafluoroethane (R-134a), a refrigerant which has been reported to have an ozone depletion potential of zero and has therefore been proposed as a replacement for the chlorofluorocarbons believed to be depleting the earth's ozone layer, e.g., chlorotrifluoromethane (R-11), dichlorodifluoromethane (R-12), and 1,2,2-trifluoro-1,1,2-trichloroethane (R-113).
PCT Application WO 90/06979 (Jolley et al.), published Jun. 28, 1990, discloses several carboxylic esters which are said to be useful as lubricants for R-134a and other halohydrocarbon refrigerants; and U.S. Pat. No. 5,021,179 (Zehler et al.) teaches certain polyhydric alcohol esters, including pentaerythritol esters, to be effective lubricants for R-134a and other fluorocarbon refrigerants.
U.S. Pat. No. 4,159,255 (Gainer et al.) discloses the use of some castor oil/neopolyol ester blends as refrigeration lubricants, while U.S. Pat. No. 4,267,064 (Sasaki et al.) teaches other such lubricants which correspond to the formula R.sub.1 [--O--(R.sub.2 O).sub.m --R.sub.3 ].sub.n and may be derived from a neopolyol or other monohydric or polyhydric alcohol. Other synthetic lubricants which can be obtained from neopolyols are some of the esters of U.S. Pat. No. 3,770,808 (Marquis et al.).